When Dieting to Lose Weight, How Much You Sleep May be as
Important as How Much You Eat

Philadelphia, October 5, 2010 - According to a
new study being published in Annals of Internal Medicine, the
flagship journal of the American College of Physicians, lack of
sleep may hinder a dieter's ability to shed excess body fat.

Ten overweight but otherwise healthy adults on a moderate
calorie-restricted diet were randomly assigned to sleep either 5.5
hours or 8.5 hours each night in a closed clinical research
environment. After two weeks, researchers measured loss of fat and
lean body mass. Compared to participants who slept 5.5 hours a
night, the dieters that slept for 8.5 hours lost 56 percent more
body fat. The dieters in the sleep restricted group had lost less
fat and more lean body mass.

"These results highlight the importance of adequate sleep for
maintenance of fat-free body mass when dieting to lose weight,"
said Plamen Penev, MD, PhD, Assistant Professor, Section of
Endocrinology, at the University of Chicago and lead author of the
study.

While measuring fat loss was the primary objective of the study,
researchers also assessed other factors including levels of
hormones that affect the appetite and weight. In addition,
participants in both groups were asked to report how much hunger
they experienced during the study.

"Among other hormonal effects, we found that sleep restriction
caused an increase in ghrelin levels in the blood," said Dr. Penev.
"Ghrelin is a hormone that has been shown to reduce energy
expenditure, stimulate hunger and food intake, promote retention of
fat, and increase glucose production in the body. This could
explain why sleep-deprived participants also reported feeling
hungrier during the study."

The researchers conclude that even short periods of sleep
deprivation can undermine efforts to lose weight. When restricting
calories, dieters should consider obtaining adequate amounts of
sleep to ensure that they retain lean body mass and lose fat.

About Annals of Internal MedicineAnnals of Internal Medicine is one of the five most widely
cited peer-reviewed medical journals in the world, with a current
impact factor of 16.2. The journal has been published for 82 years.
It accepts only 7 percent of the original research studies
submitted for publication. Follow Annals on Twitter and Facebook.

About ACP
The American College of Physicians is the largest
medical specialty organization and the second-largest physician
group in the United States. ACP members include 129,000 internal
medicine physicians (internists), related subspecialists, and
medical students. Internists specialize in the prevention,
detection, and treatment of illness in adults. Follow ACP on
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